This is exactly what you were hoping for when you overcalled preflop, except maybe for the extreme flop action in front of you. Still you're getting a good price against a very tight range even if SB doesn't call, plus that unknown with only 85bb could just be spazzing out with random stuff like AT or a lower flush draw, which you have crushed. If you don't wanna call here, consider folding that preflop next time until you have enough reads on the players that you feel comfortable calling postflop in spots like that, as it's probably as good a situation as you're gonna get with that hand in a multiway pot.